Proceedings of European Colloquium on Quantitative and Theoretical Geography, Greece, Athens, 2-5 September. GRAPH-BASED MODEL TO TRANSPORT NETWORKS ANALYSIS THROUGH GIS Paulo MORGADO 1,* , Nuno COSTA 2 1 Aux. Professor, Institute of Geography and Spatial Planning, University of Lisbon. Alameda da Universidade, 1600-214 Lisboa, Portugal. Tel. +351217940218, Email: paulo@campus.ul.pt 2 Aux. Professor, Institute of Geography and Spatial Planning, University of Lisbon. Alameda da Universidade, 1600-214 Lisboa, Portugal. Tel. +351217940218, Email: nunocosta@campus.ul.pt ABSTRACT Interest in the geographic structures of transport networks dates back the 60’s, from the economic geography studies initiated by Garrison (1960; 1961), Kansky (1963), focused almost on topologic measures. However due the limited data available and poor computing resources, geographers drive their attention to other topics, or have reveal a preference for definitions and descriptive studies over modelling and measures. More recently, mostly due the development of Geographic Information Systems and Science and geocomputation, in the 90’s, geographers become reconcile with mathematics and re-found measures in their geographic research. This paper aims to provide some insights into geographic network analysis based on an empirical study (planar and non-planar graphs) through a mathematic model (geo-graph) implemented on an ordinary GIS program as a plug-in. Subjects like the geographic implication of graph-theoretic measures, geocomputation, modelling, spatial networks analysis and small world problem of geographic networks will be mainly addressed. KEYWORDS Graph-theoretic measures, geographic networks, geocomputation, 1. INTRODUCTION It’s of course trite to say that transportation networks amplify the development of societies (Ascher, 2001) and provide the blueprint for territory organization. Hence, we could say that without transportation networks civilization as we know it could not exist (Bell and Lida, 1997). This statement frames transport networks as a geography research key subjects and explains why geographers have been the first scientists taking interest in transport networks and study their territorial impact on regional development. Although the use of computers in geography studies is not new - ever since the early 1960 quantitative geographers have replace calculators for computers in their statistical and mathematical modelling -, there’s no doubt that have been a neglect, and some biased, of the potential range of computing in doing and re-doing geography, namely on the geographic transport networks. Only recently, due the GIS revolution of the mid’s 80’s and the current high performances computing, that geography recover her quantitative legacy (Openshaw and Abrahart, 1996). There’s a natural affinity between Graph theory and Geography. In fact topology, which is a branch of mathematics that encloses graph theory, is also the foundation feature of GIS and echoes Tobler’s groundbreaking work e.g. spatial dependence, spatial interaction models and GISc (Sui, 2004). The main objective of this paper is to test these measures and analyse what spatial impact emerges from them. To do this we have build and implement a graph-based model into a GIS program, e.g. ArcGIS for try them on road networks (highway networks for planar graph measures) and on airlines networks (for non-planar graphs). The paper is organized as follows. We first outline briefly the importance of graph theory measures and networks models. Secondly, we review and present the measures integrated in the model, and what they represent for ours case studies. We then present the model architecture, cautions that have to be taken into account when preparing data for been analyzed through the model, as well the reason that explain why we have chose to develop our own model for run in a hosted GIS program instead use some other network analysis programs. Last subjects are about the main results and a last chapter for final remarks and further developments.